Nanorod semiconoductor layer having flat upper surface, mirco-led including the nanorod semiconoductor layer, pixel plate including micro-led, display device including the pixel plate, and electronic devices including the pixel plate

ABSTRACT

A nanorod semiconductor layer having a flat upper surface, a micro-LED including the nanorod semiconductor layer, a pixel plate including the micro-LED, a display device including the pixel plate, and an electronic device including the pixel plate are provided. The nanorod semiconductor layer includes: a main body; and an upper end formed from the main body, wherein the upper end includes: a first inclined surface; a second inclined surface facing the first inclined surface; and a flat upper surface between the first inclined surface and the second inclined surface, and a width of the upper end becomes narrower in an upward direction, and when a length of the upper end protruded from the main body (a thickness of the upper end) is L 1 , an inclination angle between a surface extending parallel to a surface selected from the first and second inclined surfaces and the flat upper surface is β, and a width of the main body is D, a width D 1  of the flat upper surface satisfies Equation 1. 
         D 1= D −(2× L 1×tan β)  &lt;Equation 1&gt;

CROSS-REFERENCE TO RELATED APPLICATION

This application claims is based on and claims priority under 35 U.S.C.§ 119 to Korean Patent Application No. 10-2020-0073245, filed on Jun.16, 2020, in the Korean Intellectual Property Office, the disclosure ofwhich is incorporated by reference herein in its entirety.

BACKGROUND 1. Field

The disclosure relates to nano-sized structures, and more particularly,to nanorod structures having a flat upper surface, micro-LEDs includingthe nanorod structures, pixel plates including the micro-LEDs, displaydevices including the pixel plates, and electronic devices including thepixel plates.

2. Description of Related Art

Various semiconductor materials are used in semiconductor devices. Thequality of a semiconductor material used in a semiconductor device mayaffect the operating characteristics and efficiency of the semiconductordevice. For example, the light emission efficiency of a light-emittingdevice may be closely related to the quality (thickness uniformity,composition uniformity, etc.) of a semiconductor layer used. Therefore,research to improve the quality of semiconductor materials used insemiconductor devices has been actively conducted.

SUMMARY

Provided are high-quality nanorod semiconductor layers that have a flatupper surface.

Provided are micro-LEDs that increase uniformity of thickness andcomposition of the active layer (light-emitting layer) due to use of thenanorod semiconductor layer.

Provided are pixel plates including the micro-LEDs as light-emittingelements.

Provided are display devices and electronic devices including the pixelplates.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments of the disclosure.

In accordance with an aspect of the disclosure, a nanorod semiconductorlayer includes a main body; and an upper end connected to an upper partof the main body, wherein the upper end includes a first inclinedsurface; a second inclined surface; and a flat upper surface between thefirst inclined surface and the second inclined surface, wherein a widthof the upper end becomes narrower in an upward direction away from themain body, and wherein when a thickness of the upper end in the upwarddirection is L1, an inclination angle between the flat upper surface anda surface extending parallel to a surface selected from the firstinclined surface and the second inclined surface is β, and a width ofthe main body is D, a width D1 of the flat upper surface satisfies thefollowing equation:

D1=D−(2×L1×tan β).

When a height of the main body is H, an aspect ratio (H/D) of the mainbody may satisfy 0.05<H/D<20.

H may satisfy 0.5 μm<H<20 μm.

D may satisfy 0.05 μm<D<2 μm.

The first inclined surface and the second inclined surface may include asame geometric shape.

β may be about 52±5°.

The height L1 may be about 100 nm or less.

In accordance with an aspect of the disclosure, a micro-LED includes afirst semiconductor layer of a first type including an n-type or ap-type, the first semiconductor layer including a nanorod shape; asecond semiconductor layer of a second type including the n-type or thep-type different from the first type, the second semiconductor layerfacing the first semiconductor layer; and an active layer disposedbetween the first semiconductor layer and the second semiconductorlayer, wherein the first semiconductor layer includes a main body; andan upper end connected to an upper part of the main body, wherein theupper end includes a first inclined surface; a second inclined surface;and a flat upper surface between the first inclined surface and thesecond inclined surface, wherein a width of the upper end becomesnarrower in an upward direction away from the main body, and whereinwhen a thickness of the upper end in the upward direction is L1, aninclination angle between the flat upper surface and a surface extendingparallel to a surface selected from the first inclined surface and thesecond inclined surface is β, and a width of the main body is D, a widthD1 of the flat upper surface satisfies the following equation:

D1=D−(2×L1×tan β).

The active layer may include a first compound semiconductor layer.

The active layer may further include a second compound semiconductorlayer on the first compound semiconductor layer.

The first compound semiconductor layer and the second compoundsemiconductor layer may include same materials with differentcomposition ratios.

When a height of the main body is H, an aspect ratio (H/D) of the mainbody may satisfy 0.05<H/D<20.

H may satisfy 0.5 μm<H<20 μm.

D may satisfy 0.05 μm<D<2 μm.

The first inclined surface and the second inclined surface may include asame geometric shape.

Exposed peripheral surfaces of the first semiconductor layer, the secondsemiconductor layer, and the active layer may be covered with aninsulating film.

A pixel plate may include a plurality of pixel regions, wherein each ofthe plurality of pixel regions includes a first subpixel including afirst micro-LED according to an above-noted aspect of the disclosureconfigured to emit a first light; a second subpixel including a secondmicro-LED according to an above-noted aspect of the disclosureconfigured to emit a second light; and a third subpixel including athird micro-LED according to an above-noted aspect of the disclosureconfigured to emit a third light, wherein the first micro-LED, thesecond micro-LED, and the third micro-LED each include a sameconfiguration and a same shape, and wherein the first micro-LED, thesecond micro-LED, and the third micro-LED each include differentmaterials.

Each of the first subpixel, the second subpixel, and the third subpixelmay include respective two electrodes that are parallel and separatedfrom each other, wherein the respective two electrodes are connected toeach other by a corresponding micro-LED from among the first micro-LED,the second micro-LED, and the third micro-LED.

A number of micro-LEDs included in the first subpixel may be differentfrom a number of micro-LEDs included in each of the second subpixel andthe third subpixel.

The pixel plate may further include a plurality of partition wallsprovided between adjacent subpixels from among the first subpixel, thesecond subpixel, and the third subpixel.

A display device may include a backplane; a front panel facing thebackplane; and a pixel plate according to an above-noted aspect of thedisclosure disposed between the backplane and the front panel.

An electronic device may include a front panel; a rear panel facing thefront panel; a pixel plate according to an above-noted aspect of thedisclosure disposed between the front panel and the rear panel; and abattery in contact with the rear panel.

The rear panel may include a communication module, and a camera modulemay be connected to the rear panel.

The electronic device may further include a device main body; and bandsconnected to either side of the device main body, wherein the devicemain body includes a display area including the front panel, the rearpanel, the pixel plate, and the battery, and wherein a camera, amicrophone, and a speaker are provided around the display area.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the disclosure will be more apparent from the followingdescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a cross-sectional view of a nanorod semiconductor layeraccording to an embodiment;

FIG. 2 is a cross-sectional view of a semiconductor layer furtherprovided on an upper end of the nanorod semiconductor layer in FIG. 1,according to an embodiment;

FIG. 3 is a plan view of a mask including a plurality of circularthrough-holes around a nanorod semiconductor layer according to anembodiment;

FIG. 4 is a plan view of a mask including a plurality of line-shapedthrough-holes around a nanorod semiconductor layer according to anembodiment;

FIG. 5 is a cross-sectional view of a micro-LED using a nanorodstructure according to an embodiment;

FIG. 6 is a cross-sectional view of an equivalent micro-LED showing themicro-LED shown in FIG. 5;

FIG. 7 is a plan view of a unit pixel including a micro-LED according toan embodiment;

FIG. 8 is a cross-sectional view taken along a line 8-8′ in FIG. 7;

FIG. 9 is a perspective view of a pixel plate including a plurality ofpixels according to an embodiment;

FIG. 10 is a perspective view of a display device including a pixelplate according to an embodiment;

FIG. 11 is a cross-sectional view of an electronic device having adisplay area including a pixel plate according to an embodiment;

FIG. 12 is a perspective view showing an example when the electronicdevice of FIG. 11 is a mobile phone;

FIG. 13 is a perspective view showing an example when the electronicdevice of FIG. 11 is a tablet PC;

FIG. 14 is a plan view of a smart watch as an example of an electronicdevice including a pixel plate according to an embodiment; and

FIG. 15 is a cross-sectional view taken along a line 15-15′ of FIG. 14.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments, examples of whichare illustrated in the accompanying drawings, wherein like referencenumerals refer to like elements throughout. In this regard, embodimentsmay have different forms and should not be construed as being limited tothe descriptions set forth herein. Accordingly, the embodiments aremerely described below, by referring to the figures, to explain aspects.As used herein, the term “and/or” includes any and all combinations ofone or more of the associated listed items. Expressions such as “atleast one of,” when preceding a list of elements, modify the entire listof elements and do not modify the individual elements of the list. Forexample, the expression, “at least one of a, b, and c,” should beunderstood as including only a, only b, only c, both a and b, both a andc, both b and c, or all of a, b, and c.

The advantages, features, and methods of achieving the advantages may beclear when referring to the embodiments described below together withthe drawings. However, embodiments may have different forms and shouldnot be construed as being limited to the descriptions set forth herein.Rather, these embodiments are provided so that this disclosure will bethorough and complete, and will fully convey the scope of the disclosureto those of ordinary skill in the art. Embodiments will be defined bythe appended claims. In the drawings, thicknesses of layers and regionsmay be exaggerated for convenience of explanation.

Terminologies used in the specification will be briefly described andthe current embodiment will be described in detail.

Terminologies used herein are selected as commonly used by those ofordinary skill in the art in consideration of functions of the currentembodiment, but may vary according to the technical intention,precedents, or a disclosure of a new technology. However, the terms mayhave different meanings according to the intention of one of ordinaryskill in the art, and in this case, the meaning of the selected termswill be described in detail in the detailed description of thedisclosure. Thus, the terms used herein should be defined based on themeaning of the terms together with the description throughout thespecification.

It should be understood that, when a part “comprises” or “includes” anelement in the specification, unless otherwise defined, it is notexcluding other elements but may further include other elements.

Hereinafter, a nanorod semiconductor layer having a flat upper surface,a micro-LED using the micro-LED, a pixel plate including the same, and adisplay device and an electronic device including the pixel plate willbe described in detail with reference to the accompanying drawings. Inthe drawings, thicknesses of layers and regions may be exaggerated forclarity of specification. The embodiments of the disclosure are capableof various modifications and may be embodied in many different forms. Inthe layer structure described below, when an element is referred to asbeing “on” or “above” another element, the element may be in directcontact with the other element or other intervening elements may bepresent. The electronic device may include a semiconductor device. Inthe drawings, like reference numerals refer to the like elements.

First, a nanorod semiconductor layer having a flat upper surface will bedescribed. The flat upper surface may refer to as a flat top.

FIG. 1 shows a nanorod semiconductor layer according to an embodiment.

Referring to FIG. 1, a Group III-V material layer 12 is provided on asubstrate 10. The substrate 10 may be a silicon substrate or a sapphiresubstrate, but may not be limited thereto. The Group III-V materiallayer 12 may cover an entire upper surface of the substrate 10. TheGroup III-V material layer 12 may be a doped material layer or anundoped material layer. In an example, the Group III-V material layer 12may be a doped GaN layer or an undoped GaN layer. In the case of thedoped GaN layer, the doped GaN layer may be a GaN layer doped with anN-type dopant. The Group III-V material layer 12 includes a nanorodsemiconductor layer 12A+12D formed in a direction perpendicular to theupper surface of the substrate 10 and away from the upper surface of thesubstrate 10 (i.e., in an upward direction). The nanorod semiconductorlayer 12A+12D includes a nanorod body 12A and an upper end 12D connectedto an upper part of the nanorod body 12A. The width of the upper end 12Dis gradually reduced as it goes upward. For convenience of explanation,the nanorod semiconductor layer 12A+12D is divided into the nanorod body12A and the upper end 12D, but the nanorod body 12A and the upper end12D may be a single body having the same material and compositionwithout a physical boundary therebetween. The nanorod bodies 12A areseparated at a given interval. The nanorod body 12A may have a givenheight H and a given diameter (i.e., width) D. The nanorod body 12A mayhave an aspect ratio, that is, a ratio H/D of the height H and thediameter D may be about 0.05<H/D<20. The nanorod body 12A may have adiameter D that satisfies the aspect ratio. In an example, the diameterD of the nanorod body 12A may be about 0.05 μm<D<2 μm. In addition, thenanorod body 12A may have a height H that satisfies the aspect ratio. Inan example, the height H of the nanorod body 12A may be about 0.5μm<H<20 μm.

The upper end 12D may be considered as a part grown from the nanorodbody 12A or a part protruded from the nanorod body 12A. The upper end12D includes an upper surface 12S and first and second inclined surfacesS11 and S12 on either side of the upper surface 12S. The first andsecond inclined surfaces S11 and S12 may be symmetrical about an axisextending in the upward direction with the upper surface 12S as thecenter. In an example, a geometric shape of the upper end 12D may be ahexagon when viewed in a plane. The first inclined surface S11 may havea given inclination angle β as shown in FIG. 1. The inclination angle βis an angle between a virtual inclined surface ES1 extending parallel tothe first inclined surface S11 from the first inclined surface S11 andthe upper surface 12S. The inclination angle β may be, for example,about 52±5°. Since the upper end 12D has a width gradually reducing asit goes upward, a width D1 of the upper surface 12S may be less than thewidth D of the nanorod body 12A. The width D1 of the upper surface 12Smay satisfy the following Equation 1, wherein L1 represents a thicknessof the upper end 12D.

D1=D−(2×L1×tan β)  <Equation>

FIG. 2 shows a case when a semiconductor layer 130 is provided on thenanorod semiconductor layer 12A+12D of FIG. 1. The semiconductor layer130 may be a compound semiconductor layer. The semiconductor layer 130covers the upper surfaces 12S and the first and second inclined surfacesS11 and S12 of the upper end 12D. Since an upper surface 12S of theupper end 12D is flat and the semiconductor layer 130 is present on theupper surface 12S, the semiconductor layer 130 grown on the uppersurface 12S of the upper end 12D may have a uniform thickness andcomposition. The semiconductor layer 130 may be used as a light-emittinglayer. In an example, the semiconductor layer 130 may be an InGaN layer,but is not limited thereto. When the semiconductor layer 130 is an InGaNlayer, since the semiconductor layer 130 is grown on the flat uppersurface 12S of the nanorod semiconductor layer 12A+12D, the distributionuniformity of indium In in the semiconductor layer 130 may be greaterthan when the semiconductor layer 130 is grown on a non-flat surface.Accordingly, when the semiconductor layer 130 is used as alight-emitting layer, a resultant product including the nanorodsemiconductor layer 12A+12D and the semiconductor layer 130 according toan embodiment may be used for high efficiency light-emitting nanorods.An upper surface of the semiconductor layer 130 may also be flat.

In an example, the semiconductor layer 130 may include a sequentiallystacked plurality of compound semiconductor layers. The plurality ofcompound semiconductor layers may have different physical propertiesfrom each other. In an example, the semiconductor layer 130 may be alayer formed by sequentially growing first and second compoundsemiconductor layers having different lattice constants. As the latticeconstants of the first and second compound semiconductor layers aredifferent from each other, strain may appear in the semiconductor layer130, and thus, defects may occur in the semiconductor layer 130, butsince the semiconductor layer 130 is grown on the flat upper surface 12Sof the nanorod semiconductor layer 12A+12D, the occurrence of defects inthe semiconductor layer 130 may be prevented or reduced. The first andsecond compound semiconductor layers may have the same composition(i.e., the same materials) but may have different composition ratios. Inan example, the first compound semiconductor layer may be anIn_(x)Ga_(y)N_((1-y-x)) layer (x<0.18, y>0.82), and the second compoundsemiconductor layer may be an In_(x)Ga_(y)N_((1-y-x)) layer (x>0.25,y<0.75).

FIG. 3 shows an example of a mask 14 that defines an area in which thenanorod semiconductor layer 12A+12D described above will be formed.

Referring to FIG. 3, the mask 14 includes a plurality of through holes14 h. The plurality of through holes 14 h are separated from each otherand may form an array. The through hole 14 h may be circular in a planview, but may also be in other forms, for example, oval or polygonal.

Also, as shown in FIG. 4, the through hole 15 h may be an elongatedrectangular hole or a line-shaped hole. According to the shape of themask 14, that is, according to the shape of the through hole 14 h or 15h formed in the mask 14, various nanorod semiconductor layers may beformed, and thus, the nanorod semiconductor layer formed by using themask 14 may be applied to a diffraction grating, photonic crystal, etc.by forming the through hole 14 h or 15 h formed in the mask 14 in aspecific shape.

FIG. 5 shows a micro-LED 160 as an example of a light-emitting deviceusing a nanorod structure according to an embodiment.

Referring to FIG. 5, the micro-LED 160 includes a first semiconductorlayer 162 of a first type having a pillar-shape, an active layer 164,and a second semiconductor layer 166 of a second type. The first typemay be, for example, an n-type. The second type may be, for example, ap-type. In other examples, the first and second types may be reversed.The first semiconductor layer 162, the active layer 164, and the secondsemiconductor layer 166 are sequentially stacked. In an example, thefirst semiconductor layer 162 may be a Group III-V compoundsemiconductor layer, for example, an n-GaN layer, but is not limitedthereto. The second semiconductor layer 166 may be a Group III-Vcompound semiconductor layer, for example, a p-GaN layer, but is notlimited thereto.

Other members that may stabilize the operation of the micro-LED 160,help stabilize light emission, or increase light emission efficiency mayfurther be arranged between the first semiconductor layer 162 having apillar shape, the active layer 164, and the second semiconductor layer166. The first semiconductor layer 162 having a pillar shape may be onlyan example selected from materials that are used as an n-typesemiconductor layer, for example, an n-type compound semiconductor layerof a micro-LED. The first semiconductor layer 162 having a pillar shapemay be a nanorod semiconductor layer according to an embodiment, forexample, a nanorod semiconductor layer including the nanorod body 12Aand the upper end 12D of FIG. 1. The active layer 164 may be a layerthat emits light due to recombination of holes and electrons, that is, alight-emitting layer. The active layer 164 may be a semiconductor layerhaving a multi-quantum well structure. Depending on the material of theactive layer 164, light of various wavelengths may be emitted from theactive layer 164. For example, depending on the material of the activelayer 164, the active layer 164 may be a light-emitting layer that emitsred light R, green light G, or blue light B. In one example, the activelayer 164 may be an InGaN layer, but is not limited to this material.The active layer 164 may be a single layer or multiple layers. In anexample, the active layer 164 may be a single layer compoundsemiconductor layer (InGaN). In an example, the active layer 164 may bea multi-layer compound semiconductor layer. For example, when the activelayer 164 includes the first and second compound semiconductor layers(InGaN) sequentially stacked, the composition of each layer may be thesame and the composition ratios may be different from each other. Theactive layer 164 covers an upper surface 16S3, which is flat, of thefirst semiconductor layer 162 and first and second inclined surfaces16S1 and 16S2 of either side of the flat upper surface 16S3. The activelayer 164 may be in direct contact with the upper surface 16S3 and thefirst and second inclined surfaces 16S1 and 16S2 of the firstsemiconductor layer 162. Since the upper surface 16S3 of the firstsemiconductor layer 162 having a pillar shape is flat, the compositionand thickness of the active layer 164 on the upper surface 16S3 may beuniform. Portions of the active layer 164 formed on the first and secondinclined surfaces 16S1 and 16S2 of the first semiconductor layer 162 mayhave inclined surfaces having the same inclination angles as those ofthe first and second inclined surfaces 16S1 and 16S2 within ameasurement error range. On the first and second inclined surfaces 16S1and 16S2 of the first semiconductor layer 162 having a pillar shape, theactive layer 164 may have a uniform composition and thickness. Here, thethickness may be a thickness measured in a direction perpendicular tothe first and second inclined surfaces 16S1 and 16S2. Since thecomposition and thickness of the active layer 164 formed on the uppersurface 16S3 and the first and second inclined surfaces 16S1 and 16S2 ofthe first semiconductor layer 162 having a pillar shape are uniform,light L33 of good quality may be uniformly emitted in a directionperpendicular to the upper surface of the active layer 164, and also,light L11 and L22 of good quality may be uniformly emitted in bothlateral directions of the active layer 164 (i.e., in both directionsperpendicular to the first and second inclined surfaces 16S1 and 16S2).The upper surface and both sides of the active layer 164 are coveredwith the second semiconductor layer 166. In an example, the secondsemiconductor layer 166 may cover an entire upper surface and entireside surfaces of the active layer 164 and may be in direct contact withthe upper surface and the side surfaces of the active layer 164. Thethickness of the second semiconductor layer 166 may be uniform on theupper surface of the active layer 164. The thickness of the secondsemiconductor layer 166 may be uniform on both inclined surfaces of theactive layer 164. On both inclined surfaces of the active layer 164, thesecond semiconductor layer 166 may have inclined surfaces that areparallel to both inclined surfaces of the active layer 164 or areinclined at the same angle within a measurement error range. An uppersurface 166S3 of the second semiconductor layer 166 may be parallel toor substantially parallel to the upper surface of the active layer 164.The “substantially parallel” may denote that the two upper surfaces areparallel to each other within a measurement error range such that anyangle formed between the two upper surfaces has no effect on lightemission efficiency. The second semiconductor layer 166 may be oneselected from material layers that may be used as a p-type semiconductorlayer, for example, a material layer that may be used as a p-typecompound semiconductor layer of an LED.

As may be seen in FIG. 5, the micro-LED 160 according to an embodimenthas a structure in which the active layer 164 and the secondsemiconductor layer 166 sequentially cover the upper surface 16S3 andthe side surfaces 16S1 and 16S2 of the upper end of the firstsemiconductor layer 162 having a pillar shape. Therefore, the micro-LED160 is similar in shape to a cap on the top of a pillar. The pillarportion of the first semiconductor layer 162 may perform as a pillar ofthe micro-LED 160. Except when it is necessary to distinguish, forconvenience, the upper surface 166S3 and the inclined sides of thesecond semiconductor layer 166 are considered as an upper surface andsides of the micro-LED 160. Also, a bottom surface 16S4 of the firstsemiconductor layer 162 is also considered as the bottom surface of themicro-LED 160 for convenience, except when it is necessary tospecifically distinguish.

The entire exposed surface (i.e., the peripheral surfaces) of themicro-LED 160 between the upper surface 166S3 and the bottom surface16S4 of the micro-LED 160 may be covered with an insulating film 168.The insulating layer 168 may be in close contact with the entire exposedsurface of the micro-LED 160 between the upper surface 166S3 and thebottom surface 16S4 of the micro-LED 160. The upper surface 166S3 andthe bottom surface 16S4 of the micro-LED 160 are exposed. In an example,at least a portion of both sides of the upper surface 166S3 of themicro-LED 160 may also be exposed.

FIG. 6 shows an equivalent micro-LED 170 representing the micro-LED 160shown in FIG. 5. In the drawings below, for convenience of illustration,the equivalent micro-LED 170 of FIG. 6 is used.

Referring to FIG. 6, the equivalent micro-LED 170 includes a pillar 174and a head 172. The head 172 is connected to the pillar 174 at the topof the pillar 174 to form one body. The head 172 represents the firstsemiconductor layer 162, the active layer 164, and the secondsemiconductor layer 166 sequentially stacked in the micro-LED 160 ofFIG. 5. The pillar 174 represents a pillar portion of the firstsemiconductor layer 162. The length LL1 of the pillar 174 is greaterthan the length T1 of the head 172 measured in the longitudinaldirection of the pillar 174, and is also greater than the width W1 ofthe head 172. Reference numeral 17S3 indicates the exposed upper surface166S3 of the micro-LED 160, and 17S4 indicates the exposed bottomsurface 16S4 of the micro-LED 160.

FIG. 7 is a plan view of a display device including a micro-LEDaccording to an embodiment. FIG. 7 shows a display device 180 at onepixel level.

Referring to FIG. 7, the display device 180 may be a television (TV) ora portable electronic device capable of displaying an image.

The display device 180 includes first to third subpixels 180R, 180G, and180B. The first to third subpixels 180R, 180G, and 180B are alignedparallel to each other. In one example, the first subpixel 180R may emitred light R, the second subpixel 180G may emit green light G, and thethird subpixel 180B may emit blue light B. The first subpixel 180Rincludes a first electrode 186R and a first common electrode 184R thatare separated and parallel to each other. The second sub-pixel 180Gincludes a second electrode 186G and a second common electrode 184G thatare separated and parallel to each other. The third sub-pixel 180Bincludes a third electrode 186B and a third common electrode 184B thatare separated and parallel to each other. The first to third commonelectrodes 184R, 184G, and 184B may extend to other adjacent pixels.First micro-LEDs 170R are disposed between the first electrode 186R andthe first common electrode 184R of the first sub-pixel 180R. Three firstmicro-LEDs 170R are disposed between the first electrode 186R and thefirst common electrode 184R, but the number of the first micro-LEDs 170Rdisposed between the first electrode 186R and the first common electrode184R may be one or more. The configuration and shape of the firstmicro-LEDs 170R may be the same as those of the micro-LED 170 of FIG. 6.In an example, the first micro-LED 170R may be a micro-LED emitting redlight. A head 170R-H of the first micro-LED 170R is connected to thefirst common electrode 184R, and a pillar 170R-P is connected to thefirst electrode 186R. The connection between the first micro-LED 170R,the first electrode 186R, and the first common electrode 184R may beachieved through metallization. In the metallization process, an exposedportion (upper surface) of the head 170R-H and a corresponding portionof the first common electrode 184R may be connected by covering with aconductive material (e.g., a metal), and an exposed portion (bottomsurface) of the pillar 170R-P and a corresponding portion of the firstelectrode 186R may also be connected by covering with a conductivematerial.

Second micro-LEDs 170G are disposed between the first electrode 186G andthe first common electrode 184G of the second sub-pixel 180G. Theconfiguration and shape of the second micro-LEDs 170G may be the same asthose of the micro-LED 170 of FIG. 6. In an example, the layer structureor shape of the second micro-LEDs 170G may be the same as those of thefirst micro-LED 170R except that the second micro-LEDs 170G may emitgreen light. Two second micro-LEDs 170G are arranged between the firstelectrode 186G and the first common electrode 184G, but the number ofthe second micro-LEDs 170G is not limited to two, and one or more secondmicro-LEDs 170G may be arranged. The connection relationship between thesecond micro-LED 170G, the second electrode 186G, and the second commonelectrode 184G may be the same as the connection relationship betweenthe first micro-LED 170R, the first electrode 186R, and the first commonelectrode 184R.

In the third subpixel 1806, third micro-LEDs 1706 are disposed betweenthe third electrode 186B and the third common electrode 184B. Two thirdmicro-LEDs 170B are arranged between the third electrode 186B and thethird common electrode 184B, but the number of the third micro-LEDs 170Bis not limited to two, and one or more (e.g., three, four, or five ormore) may be arranged. The configuration and shape of the thirdmicro-LED 170B may be the same as those of the micro-LED 170 of FIG. 6.In an example, the layer structure or shape of the third micro-LEDs 170Bmay be the same as those of the first and second micro-LEDs 170R and170G except that the third micro-LEDs 170G may emit blue light. Theconnection relationship between the third micro-LED 170B, the thirdelectrode 186B, and the third common electrode 1846 may be the same asthe connection relationship between the first micro-LED 170R and thefirst electrode 186R and the first common electrode 184R.

The first to third common electrodes 184R, 184G, and 1846 may include areflective material to reflect light emitted from the micro-LEDs 170R,170G, and 170B upward. For example, the first to third common electrodes184R, 184G, and 184B may include Ag, Au, Al, Cr, or Ni, or an alloy ofany two or more of these materials.

The first to third common electrodes 184R, 184G, and 184B may be groundlines. Also, there may be partition walls 194 (refer to FIG. 8) forpreventing optical interference between the first to third subpixels180R, 180G, and 1806.

FIG. 8 is a cross-sectional view taken along a line 8-8′ in FIG. 7.

Referring to FIG. 8, a plurality of driving elements 192 are present ona substrate 190. In an example, the substrate 190 may be a glasssubstrate, a sapphire substrate, or a silicon substrate coated with anoxide film. The plurality of driving elements 192 may be arranged inone-to-one correspondence to the first to third subpixels 180R, 180G,and 180B. In other words, a single driving element 192 may correspond toa single subpixel. A respective driving element 192 is arranged betweeneach of the subpixels 180R, 180G, 1806 and the substrate 190. Thedriving element 192 may drive the first to third micro-LEDs 170R, 170G,and 170B. In an example, the driving element 192 may be a thin filmtransistor. A drain of the thin film transistor 192 under the firstsubpixel 180R is connected to the first electrode 186R. A drain of thethin film transistor 192 under the second sub-pixel 180G is connected tothe second electrode 186G. A drain of the thin film transistor 192 underthe third sub-pixel 1806 is connected to the third electrode 186B. Theplurality of driving elements 192 may be provided in an array shape on aside or both sides of a pixel region of the substrate 190. In additionto the driving element 192, elements for operating and controlling of amicro-LED display may be present on the substrate 190. The substrate190, the driving element 192, and an interlayer insulating layer 188 maybe collectively referred to as a backplane 19L, and only the substrate190 and the driving element 192 may be collectively referred to as abackplane. The backplane 19L may include all elements and circuitsarranged on the substrate 190 in addition to the driving element 192.The driving element 192 is covered with the interlayer insulating layer188. A surface of the interlayer insulating layer 188 is flat, and thefirst to third subpixels 180R, 180G, and 180B are provided thereon. Forconvenience, the first to third subpixels 180R, 180G, and 180B formed onthe interlayer insulating layer 188 are collectively referred to as apixel plate 196. The pixel plate 196 may also be represented by a pixellayer.

Accordingly, the display device 180 illustrated in FIG. 8 includes thesequentially stacked backplane 19L and the pixel plate 196. The displaydevice 180 may further include a transparent front panel 198 on thepixel plate 196. The transparent front panel 198 may include ananti-reflection film attached to an outer surface thereof.

FIG. 9 shows an overall view of a pixel plate 200 included in a displaydevice according to an embodiment.

Referring to FIG. 9, the pixel plate 200 includes a plurality of unitpixel plates P1. The plurality of unit pixel plates P1 are arranged inhorizontal and vertical directions. Each unit pixel plate P1 maycorrespond to one pixel region. Each unit pixel plate P1 may be thepixel plate 196 described with reference to FIG. 8. The pixel plate 200may have flexibility. Accordingly, the pixel plate 200 may be bent orfolded.

FIG. 10 shows a display device 210 including the pixel plate 200 of FIG.9.

Referring to FIG. 10, the display device 210 includes a backplane 202, apixel plate 200, and a transparent front panel 208. The backplane 202may include a circuit unit in which elements for driving the displaydevice 210 are mounted. The circuit unit may include a semiconductorelement, for example, a TFT or a capacitor etc. for driving the pixelplate 200. The transparent front panel 208 may include a platetransparent to light, and an anti-reflection film may be provided on asurface thereof. The display device 210 may be an LED display device. Inan example, the display device 210 may constitute a display area of anelectronic device having an image display area or may be included in thedisplay area. Reference numeral 21L indicates light (e.g., an image)emitted through the transparent front panel 208.

FIG. 11 shows an electronic device 220 including a pixel plate accordingto an embodiment. The electronic device 220 may be a portable electronicdevice that may be carried by a user. The electronic device 220 has animage display area and may include a communication function. In anexample, the electronic device 220 may be a mobile phone or a tablet PC.

Referring to FIG. 11, the electronic device 220 may include a frontpanel 212, a pixel plate 214, a rear panel 216 and a battery 217. Animage formed through the pixel plate 214 passes through the front panel212 and is delivered to the user. The front panel 212 may include atransparent plate (e.g., a glass plate). The pixel plate 214 may be thepixel plate 200 of FIG. 9. The rear panel 216 is disposed behind thepixel plate 214 and may face the front panel 212 with the pixel plate214 therebetween. The rear panel 216 may include an element for drivingthe pixel plate 214 and may be a circuit board on which a module relatedto an overall operation and control of the electronic device 220 ismounted or may include such a circuit board. The battery 217 may bemounted on a portion of the rear panel 216. The battery 217 is used asoperating power of the electronic device 220. A camera module 218 isprovided on a side of the rear panel 216. Reference numeral 21Cindicates a case that surrounds a portion of the front panel 212, thepixel plate 214, and the rear panel 216.

FIG. 12 is a three-dimensional view when the electronic device 220 ofFIG. 11 is a mobile phone.

Referring to FIG. 12, the electronic device 220 has a display area 230in front thereof. The display area 230 may be at least a part of a frontsurface of the front panel 212. Reference numeral 224 indicates a frontcamera disposed above the display area 230.

FIG. 13 is a three-dimensional view when the electronic device 220 ofFIG. 11 is a tablet PC. Reference numeral 232 indicates an area in whichan image is displayed. A front camera 234 is provided above the displayarea 232.

FIG. 14 shows a smart watch 240 as an example of an electronic deviceincluding a pixel plate according to an embodiment. The smart watch 240is worn on a wrist and is a type of electronic device that providesvarious functions (e.g., bio-signal measurement function, internetconnection function, etc.) in addition to the clock and communicationfunctions.

Referring to FIG. 14, the smart watch 240 may include a main body 242(i.e., a device main body) having a display area 246 and first andsecond bands 244A and 244B that are respectively connected to eitherside of the main body 242 to attach the main body 242 to the wrist. Themain body 242 itself may be regarded as a smart watch. The main body 242is depicted in a circular shape for convenience, but may be anon-circular shape, for example, a rectangular shape. An operation stateand/or operation mode of the smart watch 240 may be displayed on thedisplay area 246 and an image may also be displayed on the display area246. The selection and control of an operation mode of the smart watch240 may be performed by touching a menu displayed on the display area246, or may be performed by using a function selection controller 24Bprovided around the main body 242. A camera 24C, a microphone 24M, and aspeaker 24S are provided around the display area 246 of the main body242. The positions of the camera 24C, the microphone 24M, and thespeaker 24S are relative and may vary, and are not limited to thoseillustrated in the drawings. A first fastening unit 248A is provided atthe end of the first band 244A connected to one side of the main body242. A second fastening unit 248B is provided at the end of the secondband 244B connected to the other side of the main body 242. When thesmart watch 240 is worn on the wrist, the first and second fasteningunits 248A and 248B may be coupled to each other.

FIG. 15 is a cross-sectional view taken along a line 15-15′ of thedisplay area 246 of the main body 242 of FIG. 14.

Referring to FIG. 15, a rear panel 252, a pixel plate 254, and a frontpanel 256 are sequentially stacked on a case 25C. The case 25C may be alower case of the main body 242. The rear panel 252 may be a circuitunit (e.g., a circuit board) in charge of an overall operation andcontrol of the main body 242 including driving and control of the pixelplate 254 or may include the circuit unit. The pixel plate 254 may bethe pixel plate 200 illustrated in FIG. 9 or may include the pixel plate200. The front panel 256 may include a plate transparent to light.

A nanorod structure according to an embodiment may have a substantiallyflat upper surface. Accordingly, in the case of a semiconductor layergrown on a nanorod structure according to an embodiment, thesemiconductor layer may have a uniform thickness and a uniformcomposition. For example, when the semiconductor layer is an InGaNlayer, an InGaN layer having a uniform thickness and a uniformcomposition of indium In may be obtained. Even when the semiconductorlayer includes sequentially grown compound semiconductor layers havingdifferent lattice constants, a semiconductor layer having no defects orreduced defects may be obtained.

In addition, the nanorod structure according to an embodiment may havevarious shapes and may be applied to a diffraction grating or photoniccrystal according to a given shape.

A micro-LED according to an embodiment is formed based on the nanorodstructure, and thus, the uniformity of the thickness and composition ofan active layer (light-emitting layer) may be increased. Accordingly, inthe case of a micro-LED according to an embodiment, it is possible toemit light of uniform intensity while increasing light emissionefficiency. Therefore, in the case of an electronic device including apixel including the disclosed micro-LED, it is possible to display animage brighter and further clearly with relatively low power.

It should be understood that embodiments described herein should beconsidered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each embodimentshould typically be considered as available for other similar featuresor aspects in other embodiments. While one or more embodiments have beendescribed with reference to the figures, it will be understood by thoseof ordinary skill in the art that various changes in form and detailsmay be made therein without departing from the spirit and scope asdefined by the following claims.

What is claimed is:
 1. A nanorod semiconductor layer comprising: a mainbody; and an upper end connected to an upper part of the main body,wherein the upper end comprises: a first inclined surface; a secondinclined surface; and a flat upper surface between the first inclinedsurface and the second inclined surface, wherein a width of the upperend becomes narrower in an upward direction away from the main body, andwherein when a thickness of the upper end in the upward direction is L1,an inclination angle between the flat upper surface and a surfaceextending parallel to a surface selected from the first inclined surfaceand the second inclined surface is β, and a width of the main body is D,a width D1 of the flat upper surface satisfies the following equation:D1=D−(2×L1×tan β).
 2. The nanorod semiconductor layer of claim 1,wherein when a height of the main body is H, an aspect ratio (H/D) ofthe main body satisfies 0.05<H/D<20.
 3. The nanorod semiconductor layerof claim 2, wherein H satisfies 0.5 μm<H<20 μm.
 4. The nanorodsemiconductor layer of claim 2, wherein D satisfies 0.05 μm<D<2 μm. 5.The nanorod semiconductor layer of claim 1, wherein the first inclinedsurface and the second inclined surface comprise a same geometric shape.6. The nanorod semiconductor layer of claim 1, wherein β is about 52±5°.7. The nanorod semiconductor layer of claim 1, wherein the thickness L1is about 100 nm or less.
 8. A micro-LED comprising: a firstsemiconductor layer of a first type comprising an n-type or a p-type,the first semiconductor layer comprising a nanorod shape; a secondsemiconductor layer of a second type comprising the n-type or the p-typedifferent from the first type, the second semiconductor layer facing thefirst semiconductor layer; and an active layer disposed between thefirst semiconductor layer and the second semiconductor layer, whereinthe first semiconductor layer comprises: a main body; and an upper endconnected to an upper part of the main body, wherein the upper endcomprises a first inclined surface; a second inclined surface; and aflat upper surface between the first inclined surface and the secondinclined surface, wherein a width of the upper end becomes narrower inan upward direction away from the main body, and wherein when athickness of the upper end in the upward direction is L1, an inclinationangle between the flat upper surface and a surface extending parallel toa surface selected from the first inclined surface and the secondinclined surface is β, and a width of the main body is D, a width D1 ofthe flat upper surface satisfies the following equation:D1=D−(2×L1×tan β).
 9. The micro-LED of claim 8, wherein the active layercomprises a first compound semiconductor layer.
 10. The micro-LED ofclaim 9, wherein the active layer further comprises a second compoundsemiconductor layer on the first compound semiconductor layer.
 11. Themicro-LED of claim 10, wherein the first compound semiconductor layerand the second compound semiconductor layer comprise same materials withdifferent composition ratios.
 12. The micro-LED of claim 8, wherein whena height of the main body is H, an aspect ratio (H/D) of the main bodysatisfies 0.05<H/D<20.
 13. The micro-LED of claim 12, wherein Hsatisfies 0.5 μm<H<20 μm.
 14. The micro-LED of claim 12, wherein Dsatisfies 0.05 μm<D<2 μm.
 15. The micro-LED of claim 8, wherein thefirst inclined surface and the second inclined surface comprise a samegeometric shape.
 16. The micro-LED of claim 8, wherein exposedperipheral surfaces of the first semiconductor layer, the secondsemiconductor layer, and the active layer are covered with an insulatingfilm.
 17. A pixel plate comprising a plurality of pixel regions, whereineach of the plurality of pixel regions comprises: a first subpixelincluding a first micro-LED according to claim 8 configured to emit afirst light; a second subpixel including a second micro-LED according toclaim 8 configured to emit a second light; and a third subpixelincluding a third micro-LED according to claim 8 configured to emit athird light, wherein the first micro-LED, the second micro-LED, and thethird micro-LED each comprise a same configuration and a same shape, andwherein the first micro-LED, the second micro-LED, and the thirdmicro-LED each comprise different materials.
 18. The pixel plate ofclaim 17, wherein each of the first subpixel, the second subpixel, andthe third subpixel comprises respective two electrodes that are paralleland separated from each other, wherein the respective two electrodes areconnected to each other by a corresponding micro-LED from among thefirst micro-LED, the second micro-LED, and the third micro-LED.
 19. Thepixel plate of claim 17, wherein a number of micro-LEDs included in thefirst subpixel is different from a number of micro-LEDs included in eachof the second subpixel and the third subpixel.
 20. The pixel plate ofclaim 17, further comprising a plurality of partition walls providedbetween adjacent subpixels from among the first subpixel, the secondsubpixel, and the third subpixel.
 21. A display device comprising: abackplane; a front panel facing the backplane; and a pixel plate ofclaim 17 disposed between the backplane and the front panel.
 22. Anelectronic device comprising: a front panel; a rear panel facing thefront panel; a pixel plate of claim 17 disposed between the front paneland the rear panel; and a battery in contact with the rear panel. 23.The electronic device of claim 22, wherein the rear panel comprises acommunication module, and wherein a camera module is connected to therear panel.
 24. The electronic device of claim 22, further comprising adevice main body; and bands connected to either side of the device mainbody, wherein the device main body comprises a display area comprisingthe front panel, the rear panel, the pixel plate, and the battery, andwherein a camera, a microphone, and a speaker are provided around thedisplay area.